Kinesin-like proteins (KLPs) play roles in several aspects of spindle assembly and chromosome segregation as well as in some non-mitotic processes (reviewed in Hirokawa et al., Curr. Opin. Cell Biol., 10:60-73, 1998). At the molecular level, all the members of this family share homology with the so-called “motor domain” of the kinesin heavy chain, which is a microtubule activated ATPase. The non-motor domain of these proteins is responsible for cargo attachment; a “cargo” can include any one of a variety of different membranous organelles, signal transduction scaffolding systems, and chromosomes. Kinesins use the energy of ATP hydrolysis to move cargo unidirectionally (toward the plus end) along a microtubule. Thus, kinesins are often called “plus-end” directed motors.
Drosophila KLP67A is a plus end-directed motor. Cytological studies have shown that KLP67A is associated with tiny 0.1 micron mitochondria at the plus-ends of the astral spindle fibers (Pereira et al., J. Cell Biol., 136:1081-1090, 1997). A human ortholog of KLP67A is KIF18A (Miki et al., Proc. Natl. Acad. Sci., USA, 98:7004-11, 2001).